Phosphine borane compounds and their preparation



United States Patent 3,086,055 PHOSPHINE BORANE COMPOUNDS AND THEIRPREPARATION Roger A. Baldwin, Robert M. Washburn, and Kendrick R. Eilar,Whittier, Califi, assignors to American Potash & Chemical Corporation, acorporation of Delaware No Drawing. Filed June 20, 1960, Ser. No. 37,08429 Claims. (Cl. 260-6065) This invention relates to a new class ofphosphine boranes useful as preignition control additives for gasoline.It is an object of this invention to provide a new class of phosphineboranes which are especially suited as preignition control additives ingasoline containing tetra-alkyl lead compounds, or equivalents, andwhich may contain ethylene dichloride and dibromide (in the case ofautomotive fuels) and ethylene dibromide alone (in the case of aviationfuels).

lt is a further object of this invention to provide a new process forthe preparation of phosphine boranes which are particularly useful aspreignition additives for gasoline.

Ancillary objects and advantages of this invention, if not specificallyset forth, will become apparent in the course of the description whichfollows.

Broadly, this invention concerns phosphin'e bor-anes of the generalformula R Ar P:BH where R represents an alkyl, cycloalkyl or aralkylgroup, where Ar is an aromatic group such as, for example, phenyl, loweralkylsubstituted phenyl, halo-substituted phenyl, naphthyl andmethoxyphenyl and n has a value of l, 2 or 3.

These materials may be added to unleaded gasoline or gasoline whichcontains TEL or similar metal-containing anti-detonant such asmethylcyclopentadienyl manganese tricarbohyl, and serve as excellentpreignition additives therein, as set forth in co-pending applicationSerial No. 796,223, filed March 2, 1959.

When the phosphine boranes of this invention are added to motor fuel,the resultant motor fuel is found to have a low preignition index and ahigh resistance to detonation knocking. Another effect of the use ofthese phosphine boranes is to decrease the tendency of the presence ofTEL, or equivalent, in the gasoline to raise the octane requirement ofthe engine in which the gasoline is used. A further advantage of thesephosphine boranes as gasoline additivesis that such phosphine boranesare highly resistant to hydrolysis, as the result of which they havelittle tendency to be leached from the [fuel by the action of such freewater as may be present. In this respect, the phosphine boranes as aclass are decidedly advantageous as compared with most other boroncontaining gasoline additives which are highly vulnerable, in mostinstances, to hydrolysis.

The phosphine boranes of this invention are also superior to the closelyrelated compounds Ar PzBX and R A1'P:BBr of the prior art in that theyare generally liquids or low melting solids, have a much highersolubility in gasoline, and are considerably more stable than the mostclosely related compounds described in the prior. art. For example, thecompounds of the present invention, when tested for hydrolytic stabilityby shaking with water (as found at the bottoms of gasoline storagetanks), were found to be considerably more stable than compounds such asThe particular physical and chemical properties of the phosphine boranesof the present invention are especially important in a gasoline additivesince additives which have low solubilities have a strong tendency toprecipitate and form solid deposits when the fuel mixture is vaporizedin the carburetor. It is desirable, but not essential, that thephosphine boranes be low-melting materials, since this property alsoreduces the tendency of the additives to precipitate and form theaforementioned solid deposits. Such deposits cause malfunctioning of theengine in addition to defeating the purpose of feeding the additive intothe combustion chamber. Liquids are also desirable from amaterial-handling standpoint since they may be blended conveniently withliquid fuels.

Also, it is self-evident that if the compounds are to be used asgasoline additives, they must be sufiiciently solu- =ble in thehydrocarbon fuel material to provide the desired results. For example,for a standard leaded gasoline containing 3 ml. per gallon of tetraethyllead, it is necessary that the phosphorus-containing additive be presentat 0.3 theory, which represents 3.07 g.-atoms of P per gallon or 0.81'g.-atorns of P per liter.

The phosphine boranes of the present invention, while suificientlysoluble in hydrocarbons, are relatively insoluble in water and this alsotends to maintain quantitative requirements at low levels since there isessentially no loss by extraction.

Various methods are available tor preparing the starting phosphines.(See Kosolapofif, Organophosphorus Compounds, John Wiley and Sons, NewYork, 1950.) For example, the following equations outline the proceduresfol-lowed for the preparation of the starting phosphincs.

A10]; RM' X ArH PO13 ArPGli AIPR: 1 ArMgX-l- P013 A131 (2) RMgX Arronanrol Ar PR 3 Several preparative methods can be used for preparing thephosphine boranes described herein; for example, the phosphonium halidecan be caused to react with a metal borohydride as typified by Equation4.

NaBH4 CgH PMeg HCl G H PMeg:BH NaCl +Ha Although this process has theadvantage that diborane does not have to be handled as shown in Equation5, it has the disadvantage of being inefiicient in consuming a mole ofhydrogen halide and the loss of a BH bond through formation of hydrogen.

A second general process involves the reaction of the phosphine withdiborane as typified by Equation 5.

representing alkyl, or in the alternative, where two or all three Rgroups together represent a single divalent radical joined to thenitrogen to form a heterocyclic ring with any remaining R grouprepresenting lower alkyl, e.g., pyridine, a lower alkyl-substitutedpyridine or N-methylpiperidine and where R, Ar and n are as definedabove. The amine borane employed is not critical; typical examples aretrimethylamine borane; triethylamine borane; tripropylamine borane;tributylamine borane; dimethylethylamine borane; butyldimethylamineborane; phenyldimethylamine borane; N-methylpiperidine borane; pyridineborane; 2-methylpyridine borane; 3-rnethylpyridine borane; or4-methylpyridine borane. Amine boranes having two and groups cannot beprepared but any of the amine boranes which may be formed worksatisfactorily.

This process also has the additional advantage that it can be simplyadapted to a continuous process for the preparation of the phosphineboranes. For example, the reaction of the amine borane and the phosphineproceeds slowly at room temperature, but becomes rapid at highertemperatures. Therefore, a mixture of the amine borane and the phosphinecan be fed to a center-feed column maintained at a convenienttemperature (-by application of vacuum), and the amine removed asdistillate from the top of the column, and the phosphine borane removedas product from the bottom of the column.

Specific examples are set forth below showing the preparation of thephosphine boranes of this invention, but these are for illustrativepurposes only and are not to be interpreted as imposing limitations onthe scope of the invention other than as set forth in the appendedclaims.

EXAMPLE I Preparation of Phenyldimethylphosphine Borane A 13.8 g. (0.1mole) quantity of phenyldimethylphosphine was mixed, under argon, with11.5 g. (0.1 mole) of triethylamine borane. The mixture was heated andtriethylamine, B.P. 88-90 C., was removed by distillation. Afterapproximately two-thirds of the amine had been distilled at atmosphericpressure from the mixture, the remainder was removed at reducedpressure. The residue was then distilled, yielding 10.7 g. (0.07 mole,70.4%) of a colorless liquid, B.P. 85-88 C. at 0.5 mm., 11 1.5504.

Analysis.-Calcd. for C H BP: B, 7.12; P, 20.38; B/P, 1.00. Found: B,7.07; P, 20.3; B/P, 0.995.

EXAMPLE II 1 Preparation of 2,5-Dimethylphenyl-Di-n-Butyl- PhosphineBorane Using the same reaction conditions as described in Example I,2,5-dimethylphenyl-di-n-butyl-phosphine borane was prepared in 83.3%yield; B.P. 140-141 C./O.5

Analysis.--Calcd. for C H BP: B, 4.10; P, 11.72; B/P=1.00. Found: B,4.08; P, 11.7; B/P=l.00l.

EXAMPLE III Preparation of Mixed mand p-EthylphenyldimethylphosphineBorane Using the same procedure and reaction conditions as described inExample I, mixed mand p-ethylphenyldimethylphosphine borane was preparedin quantitative yield; B.P. 8992 C./0.3 mm.

Analysis.Calcd. for C H BP: B, 6.01; P, 17.21; B/P=1.00. Found: B, 5.81;P, 17.22; B/P=0.966.

EXAMPLE IV Preparation of T riphenylphosphine Borane Using the samegeneral procedure used in Examples IIII, triphenylphosphine borane wasprepared in 83.3% yield; M.P. 182-184 C.

Analysis.-Calcd. for C H BP: B, 3.92; P, 11.22; B/P=1.00. Found: B,3.67; P, 11.22; B/P=0.936.

ls p-CoHsCHsCuHaP CH3 113113 (30115001141 C2115) 2 ZBl'Ia 1 CrnHrP(CeHs) 2 (1101171 C2115) 2 ZBHs CoHsP CcHn) 2 CuHsP(CoH11) e ZBHa(p-BlCoI'I4)aP (p-BrCdIflaP :BHa (D-CHaOCeHflsP (p-CHsOCuH-Qal IBHaCsHsP CHzCoHs) 2 CeHsP CHsCuHs) 2 ZBHG As aforementioned, a test forpreignition has been devised and the new compounds of this inventionhave been compared with other closely related compounds, as a result ofwhich the superiority of these compounds has been made apparent.Briefly, this test involves measuring the number of instances per unittime of motor operation in which flames occur in the combustion chamberprior to the time at which the normal flames produced by the sparkoccur, in general following the procedure described by Hirschler,McCullough and Hall, SAE Trans, 62, 40 (1954). Efficiency of thepreignition additive can be measured by the preignition index, which isa percentage of such abnormal flames occurring in the additivecontainingtest gasoline as compared with the base fuel, i.e., the sameTEL-containing gasoline which has not been treated with the preignitionadditive.

Obviously, many modifications and variations of the invention may bemade without departing from the spirit and scope thereof, and thereforeonly such limitations should be imposed as are indicated in the appendedclaims.

In the formulae used heretofore and used in the claims hereinafter, thesymbol R indicates an aliphatic radical having 112 carbon atoms such asmethyl, ethyl, cyclohexyl, and octyl. Ar represents an aromatic orsubstituted aromatic radical such as phenyl, chlorphenyl, alkoxyphenyl,halogen substituted phenyl and naphthyl.

We claim:

1. Compounds of the general formula R ,,Ar P:BH wherein R represents agroup selected from the class consisting of alkyl, aralkyl andcycloalkyl; Ar represents a group selected from the class consisting ofphenyl, lower alkyl-substituted phenyl, halo-substituted phenyl,naphthyl and methoxyphenyl and n is 1-3.

2. Compounds of claim 1 wherein R is lower alkyl.

3. Compounds of claim 1 wherein Ar is phenyl.

4. Compounds of claim 1 wherein Ar is lower alkylsubstituted phenyl.

5. Compounds of claim 1 wherein Ar is halo-substituted phenyl.

6. Compounds of claim 1 wherein Ar is naphthyl.

7. The compound phenyldimethylphosphine borane.

8. The compound 2,S-dimethylphenyl-di-n-butyl-phos phine borane.

9. The compound ethylphenyldimethylphosphine b0- rane.

10. The compound triphenylphosphine borane.

11. The compound tri(p-methylphenyl)phosphine borane.

12. The compound naphthyldiethylphosphine borane.

13. The compound bis(mcthoxyphenyl)propylphosphine borane.

14. The compound p-chlorophenyl-di-hexylphosphine borane.

15. A process for the preparation of a phosphine borane of the generalformula R Ar P:BH wherein R represents a group selected from the classconsisting of alkyl, aralkyl, and cycloalkyl, Ar represents a groupselected from the class consisting of phenyl, lower alkyl substitutedphenyl, halo-substituted phenyl, naphthyl and methoxyphenyl and n is 1-3comprising: reacting a phosphine of the general formula R Ar P with anamine borane of the general formula R N:BH wherein symbols R, Ar and nare used as previously designated and wherein R is selected from theclass consisting of three separate groups, each of said groups beingselected from the class consisting of (a) alkyl and aryl, at least twoof said groups being alkyl; (b) two separate groups, one of which islower alkyl and the other of which is an alkylene group bonded at eitherend to nitrogen; and (c) a single heterocyclic ring which, withnitrogen, forms a heterocyclic ring selected from the class consistingof pyridine and lower alkyl-substituted pyridines.

16. The process of claim 15 wherein R is lower alkyl.

17. The process of claim 15 wherein R is lower alkyl.

18. The process of claim 15 wherein Ar is phenyl.

19. The process of claim 15 wherein Ar is lower alkylsubstituted phenyl.

20. The process of claim 15 wherein Ar is halo-substituted phenyl.

21. The process of claim 15 wherein Ar is naphthyl.

22. The process of claim 15 wherein Ar is phenyl, wherein R is methyland wherein n is one.

23. The process of claim 15 wherein Ar is 2,5-dimethylphenyl, wherein Ris butyl and wherein n is one.

24. The process of claim 15 wherein Ar is p-ethylpphenyl, wherein R ismethyl and wherein n is one.

25. The process of claim 15 wherein Ar is phenyl and wherein n is three.

26. The process of claim 15 wherein Ar is p-methylphenyl and wherein nis three.

27. The process of claim 15 wherein AI is naphthyl, wherein R is ethyland wherein n is one.

28. The process of claim 15 wherein Ar is methoxyphenyl, wherein R ispropyl and wherein n is two.

29. The process of claim 15 wherein Ar is p-chlorophenyl, wherein R ishexyl and wherein n is two.

References Cited in the file of this patent UNITED STATES PATENTS2,879,301 Stewart et al. Mar. '24, 1959

1. COMPOUNDS OF THE GENERAL FORMULA R3-NARNP:BH3 WHEREIN R REPRESENTS AGROUP SELECTED FROM THE CLASS CONSISTING OF ALKYL, ARALKYL ANDCYCLOALKYL; AR REPRESENTS A GROUP SELECTED FROM THE CALSS CONSISTING OFPHENYL, LOWER ALKYL-SUBSTITUTED PHENYL, HALO-SUBSTITUTED PHENYL,NAPHTHYL AND METHOXYPHENYL AND N IS 1-3.
 15. A PROCESS FOR THEPREPARATION OF A PHOSPHINE BORANE OF THE GENERAL FORMULA R3-NARNP:BH3WHEREIN R REPRESENTS A GROUP SELECTED FROM THE CLASS CONSISTING OFALKYL, ARALKYL, AND CYCLOALKYL, AR REPRESENTS A GROUP SELECTED FROM THECLASS CONSISTING OF PHENYL, LOWER ALKYLSUBSTITUTED PHENYL,HALO-SUBSTITUTED PHENYL, NAPHTHYL AND METHOXYPHENYL AND N IS 1-3COMPRISING: REACTING A PHOSPHINE OF THE GENERAL FORMULA R3-NARNP WITH ANAMINE BORANE OF THE GENERAL FORMULA R''3N:BH3 WHEREIN SYMBOLS R, AR ANDN ARE USED AS PREVIOUSLY DESIGNATED AND WHEREIN R'' IS SELECTED FROM THECLASS CONSISTING OF THREE SEPARATE GROUPS, EACH OF SAID GROUPS BEINGSELECTED FROM THE CLASS CONSISTING OF (A) ALKYL AND ARYL, AT LEAST TWOOF SAID GROUPS BEING ALKYL; (B) TWO SEPARATE GROUPS, ONE OF WHICH ISLOWER ALKYL AND THE OTHER OF WHICH IS AN ALKYLENE GROUP BONDED AT EITHEREND TO NITROGEN; AND (C) A SINGLE HETEROCYCLIC RING WHICH, WITHNITROGEN, FORMS A HETEROCYCLIC RING SELECTED FROM THE CLASS CONSISTINGOF PYRIDINE AND LOWER-ALKYL-SUBSTITUTED PYRIDINES.